1. Field of the Invention
This invention relates primarily to locking devices for vehicle fuel tanks, particularly for trucks, to prevent fuel theft and tank tampering. The invention also relates to locking devices for stationary tanks and containers which contain fluids.
2. Description of the Prior Art
Locks for vehicle fuel tanks are well known in the art. A typical prior art tank filler cap lock is disclosed by Shaw in U.S. Pat. No. 4,377,243. The lock means is mounted within the cap secured to the tank filler tube. When the lock is actuated, copperating means and a retaining member act against the filler tube to prevent removal of the cap. In order to fill the tank, one must unlock the cap and remove it. A safety chain is provided, attached to the cap to prevent loss of the cap during filling. Another tank closure cap lock is disclosed by Gerdes in U.S. Pat. No. 4,164,302. In this invention, actuation of a cylindrical lock embedded in the center of the cap causes radial bolts to apply pressure against the retaining wall and holds the cap lock in place.
In order to fill the tank, the cap lock must be unlocked and removed. Like the shaw device, this cap lock is exposed to cold weather, allowing the locking mechanism to possibly freeze.
Yet another tank closure cap is illustrated in Rockhill in U.S. Pat. No. 1,964,214. This invention fits over the neck of a tank filler tube and depends on there being a flange or shoulder inside the filler tube, so that bolts actuated by turning a key in the lock will engage the flange, preventing removal of the cap. A hinged cover is attached to cover the top of the cap. As for the prior devices, the cap has to be removed in order to fill the tank. Thus, there exists a need for a tank filler tube locking device that does not require its removal in order to fill the tank; that can be positioned so that it is not exposed to cold climates and can be adapted to any size tank filler tube without modification of the tank filler tube.